A federal judge in Alaska has ordered Exxon to pay $4.5bn (£2.5bn) in damages for the 1989 Exxon Valdez oil spill.

In addition the group must pay $2.25bn in interest in relation to the disaster that spilled some 11 million gallons of crude oil onto the Alaskan coast.

However, Exxon Mobil, the world's largest publicly-traded oil company has said it will appeal.

The court ruling is just the latest twist in a court saga that has slowly ebbed and flowed since the early 1990s.

Dragging on

Back in 1994 a jury in Alaska ordered US giant Exxon to pay $5bn in compensation, but the firm successfully appealed.

An American federal appeals court then said the fine was excessive, and the case has dragged on pretty much ever since.

Yet David Oesting, the lawyer leading the effort against Exxon Mobil for the affected Alaskan fishermen and natives, said the latest court ruling marked "an important step forward in resolving the massive case".

He told BBC World Business Report that from the time of the oil spill to the present there has been a substantial change in the law of punitive damages.

He added: "We're definitely on track to the end of the entire dispute."

Group action

If successful, the money will be split between 32,000 fishermen, natives, land owners, small businessmen and municipalities in south central Alaska.

Exxon Mobil quickly confirmed it would be appealing.

"This ruling flies in the face of the guidelines set by the appeals court," said Charles Matthews, vice president and general counsel of Exxon Mobil.

He added: "It will, unfortunately, require us once again to appeal an order that is entirely inconsistent with the law already established."

High spirits

The Exxon Valdez tanker ran aground in Alaska's Prince Edward Sound on 24 March 1989, contaminating around 1,300 miles (2,080km) of coastline.

Its captain, Joseph Hazelwood, admitted drinking vodka before boarding the vessel, but was subsequently acquitted of operating a ship while intoxicated.

The spill killed an estimated 250,000 seabirds, 2,800 sea otters, 300 seals, 250 bald eagles, up to 22 Orca or killer whales, and an unknown number of salmon and herring.

Back in 1999 - 10 years after the spill - Exxon said the area of coastline had suffered no lasting damage.